In Canada, the most common boiler setup is the heat-only boiler, designed to provide heat exclusively to the home. These systems come in various configurations, including drafted natural vent, power vented, and condensing/direct vented. In open vent systems, exhaust gases are vented up a chimney, while indoor air is utilized for combustion. Power vent systems employ a fan motor to force exhaust gases up a chimney or out the side of the house, still using indoor air for combustion. On the other hand, condensing/direct vent systems are typically high-efficiency setups that exhaust gas outdoors and use fresh outdoor air for combustion.

Heat-only boilers focus solely on heating the home and are structured to circulate hot water through a closed-loop piping system, leading to heat emitters like radiators, in-floor heating, or air handlers. This hydronic system remains separate from the domestic water piping that fulfills the household’s plumbing needs. For added safety, a backflow preventer is included in the boiler to ensure that no water from the heating hydronic system can contaminate the municipal water system.